Green synthesis of BOSCHIBAs: Photo- and water stability, cytotoxicity assays, and theoretical calculations

Abstract

Boron Schiff bases (BOSCHIBAs) are emerging fluorescent dyes for biological and multi-stimuli applications because of the soft synthesis, low cytotoxicity, and their attractive photophysical properties. In the present work, three boron compounds (tBu2SB-BPh2 (1), MeOSB-BPh2 (2), HOSB-BPh2(3) have been synthesized by microwave-assisted synthesis and multicomponent reaction. Because of the importance of generating molecules with high chemical stability and to the interesting medical applications of fluorescent boron compounds, the photophysical properties, photostability studies, and stability in the aqueous media of all compounds were evaluated. The results show that compound 1 with tert-butyl groups is highly photostable and water-stable compared to the rest of the compounds. High-resolution mass spectrometry was also used to observe greater chemical stability of the molecular ion of 1. The high photostability and stability in aqueous media, together with the results of low toxicity, make compound 1 appropriate for biomedical application as a fluorescent biomarker. The cytotoxicity at different concentrations of some BOSCHIBAs was investigated in non-cancer (HEK-293) and cancer (B16F10) cells. The superior stability of compound 1 was confirmed by theoretical calculations, where no evidence was found to show that the chemical-structural stability is because of another characteristic, rather than protecting the fluorophore by the tert-butyl groups.